1)
Why does it say "b'Mishmar"?
1.
Ha'amek Davar: They were not sentenced to a term in prison, rather, only to stay until their judgment. Therefore they were in Beis Sar ha'Tabachim, and not in the pit with the prisoners and Yosef. 1
1
Yosef was subsequently brought out of the pit to serve them; refer to 40:4:151:1.
